Gelatin hardened with a dialdehyde-containing polymer-oxidation product of polydextrose



United States Patent 3,533,800 GELATIN HARDENED WITH A DIALDEHYDE-CONTAINING POLYMER-OXIDATION PROD- UCT 0F POLYDEXTROSE James R. King,Jr., Louis M. Minsk, and Hyman L. Cohen, Rochester, N.Y., assignors toEastman Kodak Company, Rochester, N.Y., a corporation of New Jersey NoDrawing. Filed May 2, 1966, Ser. No. 546,519 Int. Cl. G03c 1/30, 1/34U.S. Cl. 96-111 11 Claims ABSTRACT OF THE DISCLOSURE Photographicelements comprising a support having thereon a gelatin layer hardened bya dialdehyde-containing polymer-oxidation products of polydextrose aredisclosed.

This invention relates to gelatin compositions containing as a hardeningagent therein the dialdehyde of polydextrose.

The hardening of gelatin compounds with aldehydetype hardeners such asformaldehyde and the like is well known. However, in many instancesthese hardeners are unsuitable for use in photographic materialscontaining color couplers in that discoloration, e.g., a yellow strain,results from the combination of a color coupler and the aldehydehardener particularly in the case of pyrazolone couplers.

One object of our invention is to provide compositions for use inphotographic products comprising gelatin and the dialdehyde ofpolydextrose. Another object of our invention is to provide improvedhardening agents for gelatin in incorporated coupler photographicmaterials. Other objects of our invention will appear herein.

We have achieved these objects by using the dialdehyde of polydextroseas the hardening agent in gelatin compositions employed for photographicpurposes. These objects are particularly in evidence when thesehardeners are used in gelatin compositions containing or in contact withcolor couplers especialy pyrazolone couplers.

The term polydextrose, as used herein,'means a synthetic polymer ofdextrose which can be prepared using any convenient method, e.g., bypolymerizing dextrose by the procedure of P. Mora and J. Wood, Jour. Am.Chem. Soc., 80, 685 (1958). The dialdehyde of this material is obtainedby oxidizing the polydextrose such as with periodic acid or a periodatesalt which is described in U.S. Pat. 3,034,894 issued May 15, 1962. Forphotographic purposes this hardener is conveniently employed in aqueoussolution.

The hardener in accordance with our invention has varied advantages, forinstance being synthetic it avoids uncertain composition and otherdifficulties encountered with materials with natural origin. Thehardener of the invention functions actively in incorporated couplerphotographic materials without entry into stain-forming reaction withsaid couplers. Another advantage is its substantial freedom fromtoxicity. A still further advantage is that in addition to its abilityto harden gelatin the aldehyde of polydextrose displays considerableantifogging activity. A still further advantage of this hardener is theirreversible nature of the hardening action on gelatin therebypreventing migration of the hardener to other layers in multilayerphotographic products. The feature of avoiding stain with color couplersis obtained not only in cases where the couplers are incorporated in thephotographic emulsion in which the hardeners of our invention are usedbut is also noted in those cases where coupler is in solution in theprocessing baths with which the photographic products are contacted.

3,533,800 Patented Oct. 13, 1970 It is to be understood that where theterm gelatin is used herein it refers not only to gelatin per se butalso to derivatives of gelatin such as where gelatin is reacted uponwith phthalic anhydride as described in U.S. Pat. 2,525,753 or benzenesulfonyl chloride or other reactants such as described in U.S. Pat.2,614,928.

Ordinarily the use of the dialdehyde of dextrose as a hardener involvesincorporating a solution of this material in an aqueous solution ofgelatin such as a composition to be used in making photographic productsor a gelatin-silver halide photographic emulsion. Although we have notedthat just about any proportion of this hardener has a hardening effecton gelatin, it may be conveniently used by incorporating in the gelatincomposition in a proportion of about 0.1-1.0 part by weight of activealdehyde per 100 parts by weight of gelatin. We prefer to use about0.4-0.6 part by weight of active aldehyde per 100 parts by weight ofgelatin. For higher processing temperatures, it is desirable to use alarger amount of hardener.

The term poly(dialdehyde-dextrose) as used in this specificationdescribes the product resulting from the oxidation of poly(dextrose),wherein the bond between adjacent carbon atoms carrying hydroxyl groupson the sugar residue is ruptured with the formation of two aldehydegroups, and includes both the homopolymer in which all of the dextroseunits have been oxidized to the dialdehyde and also interpolymercompositions comprising oxidized and unoxidized units.

The hardener of our invention has been found to be effective as agelatin hardener not only in hardening gelatin per se but also inhardening gelatin derivatives and in hardening physical mixtures ofgelatin and gelation derivatives or with other colloids as for examplemixtures of gelatin with compatible synthetic polymers such as ethylacrylate-acrylic acid copolymer or butyl acrylateacrylic acid copolymer.The hardener in accordance with our invention has been found to beuseful for hardening amine containing polymers such as polyvinyl amine.

The following is given as an example of the preparation of a dextrosepolymer.

(A) POLYDEXTR'OSE Into a 300 ml., 3-neck flask fitted with a mechanicalstirrer, an addition funnel, an oil bath at 142 C., and a variablereflux still head attached to a vacuum pump through a Dry Ice-acetonetrap, was placed 54 g. (0.3 mole) of dextrose and 150 ml. (dry volume)of dimethyl sulfone (M.P., 109; B.P., 238 C.) or 150 ml. (liquid volume)of tetramethyl sulfone (B.P., 285 C.). This mixture was stirredvigorously and heated at 142 C. as vacuum was applied. A homogeneousmelt resulted at a vacuum of 0.7 mm. Hg. The reaction solution refluxedslowly at 120 C./0.7 mm. Hg. To this, 8.9 g. of percent phosphoric acidwas rapidly added and sulfonewater azeotrope was slowly distilled off.The polymer came out of solution slowly until stirring was no longerpossible. Distillation was continued for 45 min. at'which time thesulfone was decanted from the polymer mass. The polymeric mass wasdissolved in ml., of distilled water and isolated by pouring intomechanically stirred acetone. The precipitate was washed in freshacetone, filtered out on a Biichner funnel with suction, and dried atreduced pressure at 40 C. for 18 hours. Yield, 48.6 g. Inherentviscosity in water at 0.25 g./ 100 ml., 0.03.

The following example illustrates the preparation of a compound which isa hardener in accordance with our invention.

(B POLY DlALDEHYDE-DEXT ROSE) Into a 200 ml., 3-neck flask, fitted witha magnetic stirrer, a thermometer, and a cold water bath (at 5 C.)

were placed 100 ml., of distilled water and 47.7 g., of periodic acid(2H O) (0.21 mole). This mixture was stirred to a homogeneous solutionand cooled to C. at which time 36 g. (0.2 mole) of poly-dextrose wasadded and stirred to a homogeneous solution. The reaction solutiontemperature rose to C. then decreased to 20 C. at which time externalcooling was removed and the reaction allowed to proceed at ambienttemperature for 23 hours with stirring.

The resulting reaction mixture was poured, with mechanical stirring,into 2.5 liter of acetone. The precipitate was filtered out on a Buchnerfunnel with suction and washed repeatedly with methanol until free ofiodic acid. The washed product was dried at reduced pressure at 40 C.for 18 hours. Yield, 13.3 g.

The 13 g., of the dried oxidized poly-dextrose was dissolved in 56 g.,of distilled water, with magnetic stirring, at -95 C. The hot solutionwas filtered and stored in the refrigerator until used. Yield, 51.8 g.;solids, 12.8 percent; aldehyde content, 2.2 percent; 44.5 percentoxidized.

The following examples illustrate the use of hardeners in accordancewith our invention for the hardening of gelatin layers in photographicproducts.

EXAMPLE 1 Poly-(dialdehyde-dextrose) was added to separate portions of ahigh speed negative type gelatin-silver bromoiodide emulsion which hadbeen panchromatically sensitized by the addition of cyanine dye. Theemulsion used contained 245 grams of gelatin per mole of silver. Acontrol sample was also employed consisting of the above emulsion butwith no hardener therein. Each sample was coated on suitably subbedcellulose acetate support at a coverage of 459 mg., of silver and 1040mg., of gelatin per square foot. A sample of each coating was exposed onan Eastman 1B sensitometer, processed for 5 minutes in Kodak developerDK-50, fixed, washed and dried. The following results were obtained:

hyde dextrose), Percent Solution g. l Rel. speed Gamma Fog swell 2Control 1. 33 0. 7.50

1 Grams active polymer per 100 grams of gelatin.

2 The percent swell was determined by comparing the thickness of thesamples as measured after processing and before drying with thethickness of the photographic element before exposure and processing.

The hardener in accordance with our invention is particularly useful incolor photography especially in photographic emulsions in which a colorcoupler such as a pyrazolone coupler has been incorporated because ofthe freedom from stain when using these hardeners. The following exampleillustrates the use of the hardener of the invention in colorphotography.

EXAMPLE 2 Coatings of the following structure were applied to acellulose acetate film support in the order given. As a comparison,formaldehyde was also used as a typical aldehyde hardener.

Each hardener was employed in all six layers at a concentration of 0.5gram per 100 grams of gelatin. The layers were coated on the support inthe order given, layer 1 being immediately adjacent to the support. Eachsample was exposed and processed in the Kodak E2 Ektrachrome process. Avisual examination of the processed strips revealed the absence ofunwanted yellow stain in the sample containing poly(dialdehyde-dextrose) whereas such stain was present in the sample inwhich formaldehyde was used.

Photographic emulsions containing the hardening agents of our inventionmay be sensitized using any of the techniques well known in emulsionmaking, for example, by digesting with naturally active gelatin orvarious sulfur compounds and/or gold compounds. The emulsions may besensitized with salts of noble metals of Group VIII of the PeriodicTable which have an atomic weight greater than 100.

Silver halide emulsions containing the hardeners of the invention may beof the surface-sensitive or internally sensitive type.

The emulsions may also contain speed-increasing a'ddenda such asquaternary ammonium salts, polyethylene glycols, or thioethersensitizers.

The hardeners of the invention may be used in gelatin layers containingconventional addenda such as gelatin plasticizers, antifoggants andcoating aids. These hardeners may be useful in X-ray and other emulsionsnot spectrally sensitized. They may also be used in orthochromatic,panchromatic and infrared-sensitive emulsions. The addenda may be addedto the emulsion before or after sensitizing dyes, if any, are used.Various silver salts may be used as the sensitive salt, such as silverbromide, silver iodide, silver chloride, or mixed silver halides such assilver chlorobromide or silver bromoiodide. The hardeners of theinvention may be used in photographic elements intended for colorphotography, and which may contain color-forming couplers, or which maybe intended to be developed by solutions containing the couplers orother color-generating materials.

The hardeners of this invention are very useful in photographic elementsintended for color photography since they are compatible withhigh-boiling solvents generally used to dissolve color-forming couplers,such as the solvents disclosed in Mannes et al., U.S. Pat. 2,304,939,ssued Dec. 15, 1942, Jelley et al., U.S. Pat 2,322,027, issued June 15,1943, etc These hardeners are also compatible with low-boiling orwater-soluble organic solvents used with or in place of the high-boilingsolvents, such as those disclosed in Vittum et al., U.S. Pat. 2,801,170and Fierke et al., U.S. Pat. 2,949,360, issued Aug. 16, 1960.

In addition, the hardeners of this invention are compatible withmixtures of gelatin and dispersed vinyl poly mers Which are oftenemployed in photographic silver halide emulsions. Suitable compounds ofthis type in clude polymeric latexes of the type described, for example,in U.S. Pats. 2,272,166, 2,729,137, 2,768,080 and 3,142,568. Thehardeners of this invention may also be used with emulsions of themixed-packet type, as described in U.S. Pat. 2,698,794, or in emulsionsof the mixed grain type such as described in U.S. Pat. 2,592,243.

Emulsions obtained in accordance with our invention may be used indifi'usion transfer materials. In one common form of diffusion transferprocess, the undeveloped silver halide in non-image areas of thenegative is complexed to form a Water soluble compound which ispermitted to diffuse to a receiving layer where it is precipitated outas a metallic silver positive image. In other diffusion transferprocesses the final image is produced by diffusion of developer,oxidized developer, coupler or dye, from an exposed and developedlight-sensitive layer to a second layer in close proximity.

The invention has been described in considerable detail with particularreference to certain preferred embodiments thereof, but it will beunderstood that variations and modifications can be effected within thespirit and scope of the invention as described hereinabove, and asdefined in the appended claims.

We claim:

1. A composition of matter comprising gelatin containing a hardeningamount of a dialdehyde-containing polymer-oxidation product ofpolydextrose.

2. A composition in accordance with claim 1 in which the gelatin is acarrier for silver halide.

3. A composition in accordance with claim 1 in which the gelatin is of amodified type.

4. A composition in accordance with claim 1 in which the gelatin ismixed with synthetic water-soluble polymers.

5. A composition in accordance with claim 1 in which pyrazolone coupleris also present therein.

6. A photographic element comprising silver halide and a support havingtherein at least one gelatin layer containing a dialdehyde-containingpolymer-oxidation product of polydextrose in a concentration of fromabout 0.1 to about 1.0 weight percent of active aldehyde to gelatin.

7. The photographic element of claim 6 in which one of the layersthereon is a gelatin-silver halide emulsion containing adialdehyde-containing polymer-oxidation product of polydextrose in aconcentration of from about 0.1 to about 1.0 weight percent of activealdehyde t0 gelatin.

References Cited UNITED STATES PATENTS 3,034,894 5/1962 Jefireys et a196l 11 FOREIGN PATENTS 1,073,305 11/1960 Germany.

NORMAN G. TORCHIN, Primary Examiner R. E. FIGHTER, Assistant ExaminerUS. Cl. X.R.

